Heating unit



Jan. 14, 1958 w. H. NORTON HEATING UNIT 2 Sheets-Sheet 1 Filed April 12', 1956 WU [M172 H. Norfon Janl 'l4, 1958 w, NORTON 2,820,133

HEATING UNIT Filed April 12, 1956 2 Sheets-Sheet 2 WLl/Lam H. Norfazz b United States Patent HEATING UNIT Wi iam H. Norton, Chicfigq, 111., assignor to. Therniel, lnc'sChicago, 111,, a corporation of Illinois Application April:12, 19.56, SerialNOr. 577,855.

6 Claims (Cl- 2 9-3 This invention relates toa heating device, and more particularly, to an electrical heating unitof the type known as the metal sheath unit wherein the heating element is encased in and insulated. from a sheet of, metal.

Particularly if the metal sheath type unit is. to be ap,-- plied toa pipe or. similar conduit carrying material to be heated, it is ordinarily been found necessary to employ the metal sheath unit in the form of a split annulus, which maintains tight surface to surface contact between. the. interior heating surfaceof the metal sheath and the exterior surface of the pipe or. conduit. The unit is in the form of a split annulusin order tocompensate for differences in the coeflicients. of; thermal expansion between the metal sheath and the Pipe itself.

It has been found, however, that these metal sheath units have certain drawbacks in that heating irregularities occur because complete surface to surface contact between the metal, sheath and thepipe is lost through warpage, because ofdifferences inthe coefficients of thermal expansion of the materials involved and/or because of the split portion of the annular sheath. It will be appreciated, there can be no. surface tov surface contact between the metal sheath and the open space between contiguous faces of the sheath defining the split. This open or uncovered portion of the pipe not only does not receive heat directly from the metal sheath (by conduction), but also loses heat totheambient atmosphere (by radiation and/ or convection). Although the general nature of these difiiculties, as here expressed, has been developed primarily by hindsight, the fact that difficulties existed has been made apparent by evidence of irregularities in the heat applied around the periphery ofa pipe conducting flowing material.

The instant inventionis based in partupon the natureof the heating difficulties here involved and in part upon the discovery of means for avoiding such difiiculties. Such means involve the use of strongly resilient clamping means for obtaining complete surface to surface contact between the heating unit and theconduit at a number of diiferent operating temperatures and also for preventing warping of the unit. In addition, the instant heating unit structure also provides a split arrangement in the annular body which serves to substantiallyeliminate difficulties arising from the factthat a small portion of'the pipe or conduit is exposed by the split.

It is, therefore, an important object of the instant in: vention to provide animproved electric heating unit.

It is a furtherobject-of theinstant invention to provide a split annular-metal sheath heating. unit adapted, to be clamped on an article to be heated by means of resilient elements.

Yet anotherobject of the instant: invention is to provide an improvedv electricheater having a split annular body. carrying electrical. heating elements. thereon and adapted-to surround anarticleto be heated, saidannular body being splitfor the full length thereof at an angle with respect to its length and its. radius.

Other and further objects, features and advantages of the present invention will become apparent. to those skilled. in the art from the following detailed disclosure thereof and the drawings attached hereto and made a part hereof.

In the drawings: Figure, 1 is a view in perspective of a metal sheath type heating-unit embodyingthe instant invention;

FigureZ; is a vi'ew'comparable to Figure 1' showing a different metal sheath unit structure;

Figure 3 is a side-elevational view of one of the semi-- annular heating members of the unit shown in Figure 1';

Figure 4' is a top plan view of the embodiment of Fig-- ure 1;

Figure 5 is an elevational view of stiltanother unit:

embodying the instant invention;

Figure 6 is an enlarged sectional view taken substantially along the line VI'-.VI of Figure 5;

Figure 7 is an. enlarged detailed. view. in section taken substantially along the 1ine.VII..-.V1I of Figure 6; and

Figure 8. is; anrenlairged. detailsectional view: showing another resilient clampingarrangementembodying the, instant invention.

As shown. on; the. drawings:

in Figures 1 3 and4, anelectric heater indicatedgenr lly by: he reference numeral. 10 emb ying: h nstant invention as a split annular body 11. Actually, the body it is formed by'apair 11a, 11b of allochiral semi-annular heating members separably secured together to define an annulus adapted to. surround a pipe, 12 or similar article.-

to be heated. The; pipe 12 preferably receives the fluid material flowing therethrough so as to. continuously heat the same. via the, heating unit 10.. As will be noted, the annular body 11 is; split along. the splits 3-1 and 8-2 for the full length thereof at an angle with respect to its length and its radius. Each of the semi-annular heating members. 11a,v and 111') carries electrical heating elements. some of which are. indicated at 13a and 1315. Although the, particular design of the heating element here employed does not form a. critical part, of the instant invention since made of stainless steel and it is embedded in the member- 11!) which is made of extruded aluminum.

In this way an electric current source (not shown) may be applied to the Nichrome wirewhich in turn forces heat through the sleeve 13a and the body 11b to the inner peripheralheating surface 10a of the heater 10. The inner peripheral heating surface 10a ofthe heater 10 is in substantial surface to surface contact with the outer periphery of the pipe 12' so that heat passes thereacross through conduc-. tion.

Stainless steelor similar structural bands 14a and 1411" are wrapped around the members 11a and 11b and resiliently urged together by spring urged bolt and nut assemblies 15a and 15b. As indicated, the band 14b is.

flanged at its extremities 16, 16 and a bolt 17 passes through thefianges 16, 16' and engages a lock nut 18 at one side. as to draw the flanges 16, 16 together. means are shown in Figures 5 through 8.

In the instant invention, it has been found particularly. important to employ resilient clamping means, such as.

the means 1521, 15b, in order to continuously urgethe,"

Pa ented Jan. 1 ,1958.

The lock nut l8 is urged by a spring 20 so...

Other resilient.

members 11a and 11b into surface to surface contact with the pipe 12. The resilient means 15a, 15b employed are capable of applying substantial forces through the spring 20, 20, but the resilient means 15a, 15b are fully capable of yielding to expansion of the pipe 12 as a result of heating thereof.

Referring now to Figure 4 (wherein the heating elements 13a, 13b and the clamping means 14a, 14b are omitted for simplification) it will be seen that the splits S-1 and 8-2 extend at an angle to the annulus radius R-l. Since it is preferable to have the split S2 lie along a substantially straight line (in the plan view of Figure 4), the split S2 must form an angle A of at least 90 with the radius R-1 and the angle is preferably 90 to about 150". This is actually an average range for a given split, since the angle A is changed with a straight line split 8-1 from the top to the bottom of the annular body 10, if the split 8-1 is also aligned angularly with respect to the length of the annular body 10. The alignment of the split S2 angularly with respect to the radius R-l results in a distinct improvement in the operation of the unit 10, because heat losses through radiation and convection at the portion of the pipe 12 exposed by the split 8-2 are minimized. Also, because of the relatively thin (unsupported) lip portion 110 of the member 11b which is the overlapping portion for the split S2, it will be appreciated that very close contact between the ele- .ments 11a and 11b may be maintained continuously; in fact, these elements 11a and 11b may almost touch because the lip portion 110 can be formed to yield slightly to the forces of thermal expansion and contraction. In this way the split 3-2 is substantially closed.

Referring now to Figure 3, it will be seen that one of the contiguous face portions 11d (of the member 11b) extends at an angle to the annulus length L-1. The split 8-1 will, of course, also extend at the angle B that the face portion 11d forms with the annulus length L-1. Although the angle B could possibly be as much as 90 in a generally spiral configuration for the split S-l, it is preferable to maintain the angle B within the range of 5 to about 30 for units having a reasonable length (but in the case of extremely short units the angle B may be as much as 45 or 60). The result of having the split 8-1 (for the face portion 11d) at an angle to the length L-1 (taken along the peripheral surface of the body 11b) is that the portion of the pipe 12 exposed by the split 8-1 is located at a different peripheral or angular position with respect to the pipe 12 throughout the length of the heating unit 10. This has been found to be particularly important in the case of extreme operating conditions. In such circumstances a liquid material which may freeze rather easily can possibly freeze and deposit on the inside of the pipe in alignment with a longitudinally extending split, because heat cannot be conducted fast enough to this region of the pipe and/or heat losses through convection or radiation are excessive at this region.

It will be appreciated that the split S-l can extend at an angle to the annulus radius R-1 and be aligned with the length L-l, or vice versa, so as to obtain distinct advantages in the practice of the instant invention; but it is preferred to have the split S-l extend at an angle to both the radius R-1 and the length L-1 of the annular member 10. In this preferred arrangement the best heating conditions are obtained.

It will also be appreciated that an annular heating unit 100, as shown in Figure 2, may be formed with only a single split S-100 to provide a suitable heating unit embodying the instant invention. In Figure 2, elements corresponding to those shown in Figures 1, 3 and 4 are indcated with the same reference numeral in the 100 series. The single split 8-100 is, like the split 8-1 of Figure ,1, formed so as to extend the full length of the 4 annular body at an angle with respect to its length and its radius; and the split 8-100 is also formed so as to permit relative expansion and contraction between the body 100 and the pipe 112. The suitable resilient clamping means in the form of the bands 114a and 114b and the resilient clamping units 115a and 11511 serve to resiliently urge the split 8-100 closed. It is preferable to employ a pair of heating unit members 11a, 11b for the reason that no strain or bending is required in the unit 11 during expansion and contraction thereof.

Referring now to Figure 5 and Figures 6 and 7 which show details thereof, it will be seen that the unit 200 of Figure 5 comprises a pair of allochiral semi-annular heating members 211a and 211b secured together to define the annulus, each carrying electrical heating elements 213a through 213k. The annulus 200 is split at 8-201 and S-202 (Figure 6) along the full length of the annulus 200 at an angle to the annulus length and the annulus radius in the manner hereinbefore described.

As shown in Figures 5, 6 and 7, the heating element 213g is embedded in the semi-annular heater member 211a and is turned radially outwardly at the splits 8-201 and S-202 to define leads F, F which may be connected to a source of electricity (not shown). As indicated in the sectional view of Figure 7, the sleeve unit 213g comprises a stainless steel sleeve 230 having an elongated helical resistor 231 of Nichrome wire closely surrounded by the sleeve 230 which carries electrically insulative refractory particulate material 232 for maintaining the resistor 231 in closely spaced relation to the sleeve 230. As shown in Figure 6, leads f extend out of the turned portions of the sleeves F, F; and these leads f, f are connected to the Nichrome wire 231. In a similar manner the heating element 2130 is embedded in the semi-annular member 211b and has ends E, E turned outwardly. The outwardly turned ends C and D of the heating elements 213k and 213d, respectively, are also shown in Figures 5 and 7. As indicated, the structures of all of the outwardly turned heating element ends, C, D, etc. are the same. Although the clamping means is not shown in Figure 5, it will be noted that similar structures are indicated for the heating elements 213a, 213b, 213e and 213 which are clamped together by means (not shown) having the same structure as means 233 which clamp together the end members C, D, E, and F. Referring in further detail to Figure 7, it will be seen that the resilient clamping means 233 comprise a first bracket 234 held against the backs of the leads E and F and a second bracket member 235 held against the backs of the leads C and D. A tie rod 236 is slidably received by the brackets 234 and 235. A first spring 237 backed against a lock nut 238 at one end of the tie rod 236 and second spring 239 backed against a lock nut 240 at the opposite end of the tie rod 236 serve to urge the bracket members 234 and 235 together and thus resiliently clamp the semiannular elements 211a and 21117 together. A comparable resilient assembly 233a is employed for retaining the leads E, F, etc. resiliently as indicated at the left hand side of Figure 6. Such resilient clamping means 233, 233a, etc. serve to separably retain the members 211a, 211b in position during expansion and contraction thereof.

In Figure 8, a detail of another clamping arrangement 250 is shown. In the arrangement 250 semi-annular members 251a and 25115 are positioned so as to define an angularly aligned split 8-250 in the manner hereinbefore described and heating elements 252a and 252b, respectively, are embedded therein in substantially the manner hereinbefore described. The heating elements 252a and 252b, however, are connected at their ends to contact bars 253a and 253b which are in turn connected to a source of electric power (not shown) for energizing the heating units 252a and 252b. Also, the

units 252a and 252!) are mounted in open grooves in the elements 251a and 251!) and are retained therein (as if embedded therein) by stainless steel bands 254a and 2541; wrapped around the backs of the members 251a and 251b, respectively and fianged at their ends g and h, respectively, so as to slidably receive a tie rod 255 which mounts lock nuts 256 and 257 at the ends thereof urged by springs 258 and 259 backed against the flanges g and h, respectively, so as to urge the flanges together resiliently.

It will be understood that modifications and variations may be efiected without departing from the scope of the novel concepts of the present invention.

I claim as my invention:

1. An electric heater having a split annular body can rying electrical heating elements thereon and adapted to surround an article to be heated, said annular body being split for the full length thereof at an angle with respect to its length and its radius.

2.v An electric heater having a split annular body carrying electrical heating elements thereon and adapted to surround an article to be heated, said annular body being split for the full length thereof at an angle with respect to its length.

3. In an electric heater, a pair of allochiral semi-annular heating members separably secured together to define an annulus, each carrying electrical heating elements, the

contiguous faces of said members extending at an angle to the annulus length.

4. In an electric heater, a pair of allochiral semi-annular heating members separably secured together to define an annulus, each carrying electrical heating elements, the contiguous faces of said members extending at an angle to the annulus length and the annulus radius.

5. In an electric heater, a pair of allochiral semiannular heating members, resilient means urging the members together to define an annulus, each carrying electrical heating elements, the contiguous faces of said members extending at an angle to the annulus length.

6. In an electric heater, a pair of allochiral semiannuluar heating members, resilient means urging the members together to define an annulus, each carrying electrical heating elements, the contiguous faces of said members extending at an angle to the annulus length and the annulus radius.

References Cited in the tile of this patent UNITED STATES PATENTS 2,510,456 Biebel June 6, 1950 2,725,457 Norton Nov. 29, 1955 FOREIGN PATENTS 351,595 Germany Mar. 12, 1921 

